This invention relates generally to washing machines, and more particularly, to systems and methods for accelerating an unbalanced washer basket.
Known washing machines typically include a cabinet that houses an outer tub for containing wash and rinse water, a perforated laundry item basket within the tub, and an agitator within the basket. A drive and motor assembly is mounted underneath the stationary outer tub to rotate the basket and the agitator relative to one another. Water is extracted from the laundry items by revolving the perforated laundry item containing the laundry items at a high rotational velocity. Centrifugal forces pull the majority of the water out of the laundry items and through the holes in the rotating basket. A pump assembly pumps water from the machine to a drain to execute a wash cycle. In known washing machines the rotating basket is supported by a suspension system designed to dampen translational motion induced by any imbalance with in the rotating basket. High stresses are sometimes encountered within the basket, drive system, and suspension system during the high-speed spin action used for water extraction during normal wash cycles. With an imbalance within the load, a force is generated which is proportional to the product of the mass, the distance between the imbalance and the center of rotation, and the square of the velocity. Small imbalances can very easily generate large forces as a result of the high rotational velocities.
Some known washing machines may employ a sensor to determine if the machine is operating with an unbalanced load. If an unbalanced load is detected during an extraction spin cycle, the machine is stopped and a signal is generated to alert the user to the unbalanced load. Other machines are configured to measure the unbalance and then decide if the unbalance is too large or if it is desirable to increase speed. For spin speeds in excess of 630 rpm, the basket speed must be prevented from exceeding the design limits of the basket. At low speeds, motor load cannot be used to determine an unbalance because a brake drag provides a load on the motor in addition to the load provided by any imbalance.